The present invention is directed to a process for the drying of wet loose material, in particular coke powder or fines, with the help of a heat source such as a burner and its flue gases. According to the invention, the material rotates about an axis aligned with the burner flame and the stream of the flue gases and travels along the axis so as to begin its rotation and movement in an opposing direction to the flue gas. The material is subjected to predrying. The vapor produced by predrying moisture out of the material is entrained in the flue gases. Subsequently the material is further dried to a terminal moisture level. The invention is also directed to apparatus for carrying out this process.
An example of loose material which can be dried in accordance with the invention is salt or sand but preferably mineral fuels, such as coal having a fluid consistency and above all, coke fines. Without exception, these materials set free considerable amounts of dust as soon as they have been deprived of a predetermined amount of moisture. Particularly large amounts of dust develop, as is known from experience, with the drying of coke fines. Because of the properties of coke fines, this dust is particularly undesirable and results in considerable pollution of the environment when placed in the atmosphere.
The existence of a process of the type described above is known and is carried out with apparatus having a wet material inlet, a drying outlet, and a rotatable inner drum which incorporates a heat source and/or hot gases. On an end of the drum, wall perforations are provided for the discharge of the material. A casing is provided which is arranged concentrically to the inner drum and which provides on the drum end, a removal pipe which opens into the space between the drum and the casing.
According to the known process the wet material is predried in the front part of the inner drum through the direct action of the flue gases of the burner. Consequently, the vapor originating by the predrying of the moisture out of the material becomes entrained in the flue gases.
In an attached section of the inner drum adjacent to the burner, the material is then further dried. The vapor produced by this drying likewise becomes entrained in the flue gases. The corresponding gas mixture formed out of the flue gas and the vapor is conveyed out of the inner drum in the space between the drum and the casing to communicate the waste heat on the wall on the inner drum.
With the foregoing process, it is technically necessary to employ dust collection equipment because of the considerable quantity of dust which is set free as soon as the material reaches its terminal moisture. This dust passes initially in the flue gas-water vapor mixture and arrives at the outlet of the gas stream. On the basis of emission protection, dust collection equipment cannot be done without. The dust development by the rotation and movement of the material dried down to its end moisture within the entire process cannot be avoided. There results, before long, disadvantages.
The process is encumbered with the dust collection equipment which causes considerable technical and economic expense. Additionally, the dust contained in the vapor causes difficulty within the process and accumulates in a form which, as a rule, excludes further direct mechanical treatment.